Catheter having increased curve performance through heat treatment

ABSTRACT

The present invention includes catheters and catheter shafts having a curved portion, for example, a curved distal portion. The curved distal portion may be formed by subjecting the distal portion, which might include one or more polymeric segments or layers, to heat at or above the melt temperature thereof. Heating at or above the melt temperature may reduce residual stress and eliminate heat history.

RELATED APPLICATIONS

This application is a continuation of co-pending U.S. application Ser.No. 09/957,361, filed Sep. 20, 2001, the entire disclosure of which isincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to catheters for performingmedical procedures. More particularly, the present invention relates tointravascular catheters having a curved portion.

BACKGROUND OF THE INVENTION

A wide variety of intravascular catheters have been developed todiagnose and treat vascular diseases. Some types of catheters include acurved or shaped distal portion in order to facilitate navigation of thecatheter through the vasculature. Formation of the curved portionusually comprises shaping and heat treating the distal end of thecatheter below the melting point of the polymers contained therein,which may result in undesirable physical properties.

SUMMARY OF THE INVENTION

To reduce or eliminate such undesirable physical properties, the presentinvention provides design and manufacturing alternatives for cathetershaving a shaped or curved portion as described in more detailhereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a catheter including a shaped distal portionaccording to an embodiment of the invention, together with a retentionsleeve;

FIG. 2 is an enlarged view of the shaped distal portion of the cathetershown in FIG. 1, together with a retention sleeve and a forming mandrel;and

FIG. 3 is a cross-sectional view of FIG. 2 taken along line 3-3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description should be read with reference to the drawingswherein like reference numerals indicate like elements throughout theseveral views. The detailed description and drawings illustrateembodiments by way of example, not limitation.

FIG. 1 is a plan view of a catheter 10 comprising an elongate shaft 12having a proximal end 14, a distal end 16, and a shaped distal portion20. Shaped distal portion 20 includes at least one polymeric segmentand/or layer which allows the distal portion 20 to be formed by shapingand heat treating it to a temperature above the melting point of one ormore of the polymeric segment(s) and/or layer(s). It is believed thatheat treating to temperatures above the melting point of the polymericsegment(s) or layer(s) of the distal portion 20 may eliminate heathistory, residual stress, and morphological orientation and may restorethe original physical properties of catheter 10. Such heat treating isnot limited to the distal portion 20, but may be equally applicable toany portion of catheter 10, including shaped and straight portions, toeliminate heat history, residual stress, and morphological orientation.

As used herein, heat treating is understood to be mean a thermal processof exposing or generating heat in the polymeric segment(s) or layer(s).Heat treating may be accomplished by a number of methods and techniques.For example, heat treating may include exposure of the polymericsegment(s) or layer(s) of the distal portion 20 to infrared energy,radio frequency electromagnetic energy, radiant heating, laser energy,etc. Alternatively, the polymeric segment(s) or layer(s) of the distalportion 20 may be placed into an oven or a die that is coupled to a heatsource. A person of ordinary skill in the art will be familiar with heattreating techniques appropriate for multiple embodiments of theinvention.

Catheter 10 may comprise any one of multiple different catheter types.These catheter types include, but are not limited to, a guide catheter,a diagnostic catheter, a balloon catheter, an atherectomy catheter, etc.A person of ordinary skill in the art will be familiar with differenttypes of catheters appropriate for multiple embodiments of the presentinvention. For purposes of illustration only, catheter 10 is depicted inFIG. 1 as a guide catheter.

A manifold 18 may be disposed at proximal end 14 of elongate shaft 12.Manifold 18 may comprise a single-port adapter (as shown) for a guidecatheter, or a double-port adapter, a multi-port adapter, a connector,etc., depending on the type of catheter selected. A therapeutic ordiagnostic device (not shown) such as an inflatable balloon or arotating burr may be connected to distal end 16 of elongate shaft 12,depending on the type of catheter selected. The elongate shaft 12 mayalso incorporate one or more lumens and/or mechanisms necessary tooperate such therapeutic and diagnostic devices.

Elongate shaft 12 may be generally tubular and may be manufactured froma number of materials including, but not limited to, polymers such aspolyoxymethylene (POM), polybutylene terephthalate (PBT), polyetherblock ester available under the trade name ARNITEL, polyether blockamide (PEBA), fluorinated ethylene propylene (FEP), polyethylene (PE),polypropylene (PP), polyvinylchloride (PVC), polyurethane,polytetrafluoroethylene (PTFE), polyether-ether ketone (PEEK),polyimide, polyamide, polyphenylene sulfide (PPS), polyphenylene oxide(PPO), polysufone, nylon, and perfluoro(propyl vinyl ether) (PFA);polymer/metal composites including any of the polymers described abovein combination with a metallic reinforcement such as a coil or braidformed of stainless steel, nickel alloy, or nickel-titanium alloy; andcombinations thereof. Elongate shaft 12 may be manufactured so as tomaintain a level of flexibility and torquability appropriate formaneuvering catheter 10 through the vasculature. For example, shapedportion 20 may comprise a polymer/metal composite having an innerlubricious polymer layer (e.g., PTFE), an intermediate reinforcementlayer (e.g., SST braid), and an outer polymeric layer (e.g., PEBA) tofacilitate thermal processing as described in more detail below.

The shaped distal portion 20 is conventionally included to aid in theadvancement of catheter 10 through the vasculature. For example, theshaped distal portion 20 may aid navigation of the catheter 10 over theaortic arch to access a coronary artery. The shaped distal portion 20 istypically formed by shaping and holding the catheter 10 in aconfiguration having a curve near distal end 16 and then heat treatingcatheter 10 to a temperature below the melting point of all polymerscontained in the shaft 12.

Such shaping and heat treating of the catheter 10, followed by coolingthereof, imparts and maintains the shape or curve of the distal portion20. However, such shaping and heat treating catheters may also lead tochanges in the physical properties of catheter 10. For example, shapingand heating may increase the residual stress, alter the morphologicalorientation of particles within elongate shaft 12, and/or alterstiffness of elongate shaft 12. Changes in these and other physicalproperties may compromise the intended physical characteristicscontemplated during the design of catheter 10.

It is therefore desirable, in some cases, to restore the virgin ororiginal characteristics of the polymeric materials contained within theshaped distal portion 20 or other portions of the elongate shaft 12.Although annealing, tempering, or other similar thermal processingtechniques may be utilized to alleviate a limited amount of residualstress and restore to a limited degree the original morphologicalorientation, such techniques only heat the polymeric materials to atemperature below the melting point thereof, which may not completelyaccomplish the objective. Thus, heat treating the distal portion 20 orany other portion of the shaft 12 to a temperature below the meltingpoint of the polymers contained therein may be sub-optimal and maycompromise the intended performance of the catheter 10.

To avoid such a compromise, the present invention provides design andmanufacturing alternatives for constructing catheter 10 having a distalshaped portion 20 that is formed by thermal processing above or equal tothe melting temperature of the polymers contained therein.

For example, if the polymer(s) of the distal portion 20 comprise a blendof 10% ARNITEL brand polyether block ester and 90% PBT, the distalportion 20 may be heated to a temperature of 480° F. for 2 minutes tohave the desired effect. Also by way of example, if the polymer(s) ofthe distal portion 20 comprise DELRINE brand POM, the distal portion 20may be heated to a temperature of 400° F. for 4 minutes to have thedesired effect.

Because heat treating the shaped distal portion 20 involves raising thetemperature of the polymers contained therein to a point greater than orequal to the melting point thereof, it may be desirable to utilize aretention sleeve 22 during the thermal processing. The retention sleevefunctions to maintain the outer shape and structure of the distalportion 20 and to prevent the molten polymers from flowing. The sleeve22 may extend over all or a portion of the elongate shaft 12, dependingon the length of the shaft 12 exposed to the heat. After thermalprocessing and cooling, the sleeve 22 may be removed or left thereon toreduce polymeric creep (i.e., to retain the shape of the distal portion20).

As mentioned above, one of the purposes for including sleeve 22 is tomaintain the shape and structure of elongate shaft 12 during heating.Because the temperature of elongate shaft 12 may equal or exceed themelting point of the polymers contained therein, molten polymericportions of elongate shaft 12 may flow and cause unwanted deformation.The sleeve 22, thus, provides a physical barrier for preventing moltenor partially molten portions of elongate shaft 12 from flowing away fromtheir intended position and thus preserves the shape and structure ofthe outside surface of catheter 10. To better serve this function, thesleeve 22 may have a melting temperature that is greater than that ofthe polymeric materials of elongate shaft 12 being heat treated. Thesleeve 22 may comprise, for example, a heat shrink tube made offluorinated ethylene propylene.

FIG. 2 is an enlarged view of the shaped distal portion 20, togetherwith the sleeve 22 and a mandrel 28. The mandrel 28 may be disposedwithin the elongate shaft 12 (e.g., within a lumen of elongate shaft 12)to extend through the distal portion 20 and/or other portions of theshaft 12 subject to heat treatment. As with the sleeve 22, the mandrel28 provides a physical barrier to prevent molten or partially moltenportions of elongate shaft 12 from flowing away from their intendedposition and thus preserves the shape and structure of the insidesurface of catheter 10. The combination of the sleeve 22 and the mandrel28 provide barriers for both the inside surface and the outside surfaceof the portion(s) of the elongate shaft 12 subject to heat treatment.

FIG. 3 is a cross-sectional view of FIG. 2 taken along line 3-3. In thisillustration, the shaped distal portion 20 of the catheter shaft isdisposed over the mandrel 28. The catheter shaft includes an innerpolymeric layer 34 having a melt temperature and an outer polymericlayer 36 having a different melt temperature. Sleeve 22 is also seen.The shaped distal portion 20 can be subjected to heat that is at orabove the melt temperature of the inner polymeric layer 34. The shapeddistal portion 20 can be subjected to heat that is at or above melttemperature of the outer polymeric layer 36. The shaped distal portion20 can be subjected to heat that is at or above the melt temperature ofthe inner polymer layer 34 and that is at or above the melt temperatureof the outer polymeric layer 36.

As mentioned previously, the entire shaft 12 may be subject to heattreatment, or the heat treating process may be localized to a portion ofelongate shaft 12. For example, heat exposure or generation may occuronly along portions of elongate shaft 12 where the sleeve 22 is disposedthereon. In other words, the heat treatment zone may be limited to theregion between the proximal 24 and distal 26 ends of the sleeve 22. Whenutilizing localized heat treatment, the unheated portions of the shaft12 serve to limit molten polymer flow at the respective ends of the heattreatment zone.

For example, the heat treatment zone may be limited to a region betweenthe proximal end 24 and distal end 26 of the sleeve 22. In thisscenario, the length of the elongate shaft 12 not covered by the sleeve22 would not be subject to heat treating, and thus would not be molten.These non-molten sections of elongate shaft 12 serve as a barrier forpreserving the shape and structure of elongate shaft 12 at the ends ofthe heat treatment zone. When the sleeve 22 and the mandrel 28 are usedin this scenario, essentially all sides of elongate shaft 12 subject toheat would have structural support during heat treatment.

If the entire length of the shaft 12 were exposed to heat, or iflocalized heat were applied to the distal end 16 of the shaft 12, therewould not be a non-molten portion of the shaft 12 at the distal end ofthe heat treatment zone. In this scenario, a cap 30 coupled to a distalend 32 of the mandrel 28 may be used to prevent the flow of moltenpolymeric material at the distal extremity 16. In this embodiment, thecap 30 may abut the distal end 16 of elongate shaft 12 and the distalend 26 of the sleeve 22 to provide structural support. Alternatively,the sleeve 22 may incorporate an inward facing flange at the distal end26 thereof to serve the same function. Those skilled in the art willrecognize alternative designs and arrangements to accomplish the samefunction.

It should be understood that this disclosure is, in many respects, onlyillustrative. Changes may be made in details, particularly in matters ofshape, size, arrangement of parts and order of steps without departingfrom the scope of the invention. The invention's scope is, of course,defined in the language in which the appended claims are expressed.

1. A method of manufacturing an intravascular catheter, comprising thesteps of: providing a relatively straight elongate shaft having aproximal end, a distal end and a distal portion, the distal portionincluding a polymer having a melt temperature; shaping the distalportion; and after the step of shaping the distal portion, heating theshaped distal portion to a temperature at or above the melt temperature,wherein the step of shaping the distal portion imparts residual stressin the distal portion, and wherein the step of heating the shaped distalportion results in the shaped distal portion being generally free ofsaid residual stress.
 2. The method of manufacturing an intravascularcatheter as in claim 1, wherein the shaped distal portion is heated to atemperature below the melt temperature and allowed to cool in order toset the shape of the distal portion prior to the step of heating theshaped distal portion to a temperature at or above the melt temperature.3. The method of manufacturing an intravascular catheter as in claim 1,further comprising the steps of: providing a sleeve; and placing thesleeve about the shaped distal portion prior to heating.
 4. The methodof manufacturing an intravascular catheter as in claim 3, furthercomprising the steps of: providing a mandrel; and placing the mandrel inthe shaped distal portion prior to heating.
 5. The method ofmanufacturing an intravascular catheter as in claim 4, wherein themandrel has an end cap, and wherein the mandrel is placed in the shapeddistal portion such that the cap abuts the distal end of the shaft. 6.The method of manufacturing an intravascular catheter as in claim 1,wherein the step of shaping the distal portion includes the steps of:imparting a curve to the distal portion; and setting the curve.
 7. Themethod of manufacturing an intravascular catheter as in claim 3, whereinduring the step of heating the shaped distal portion, the shaft extendsdistally and proximally of the sleeve.
 8. The method of manufacturing anintravascular catheter as in claim 1, wherein the heating is localizedto the distal portion of the shaft.
 9. The method of manufacturing anintravascular catheter as in claim 3, further comprising the step of:after the step of heating the shaft, cooling the shaft; and aftercooling the shaft, removing the sleeve.
 10. The method of manufacturingan intravascular catheter as in claim 3, further comprising the step of:after the step of heating the shaft, cooling the shaft; and aftercooling the shaft, retaining the sleeve.
 11. A method of manufacturingan intravascular catheter, comprising the steps of: providing arelatively straight elongate shaft having a proximal end, a distal endand a distal portion, the distal portion including a polymer having amelt temperature; shaping the distal portion; heating the shaped distalportion to a temperature at or above the melt temperature, wherein theshaped distal portion is heated to a temperature below the melttemperature and allowed to cool in order to set the shape of the distalportion prior to the step of heating the shaped distal portion to atemperature at or above the melt temperature, wherein the step ofshaping the distal portion imparts residual stress in the distalportion, and wherein the step of heating the shaped distal portionresults in the shaped distal portion being generally free of saidresidual stress.
 12. The method of manufacturing an intravascularcatheter as in claim 11, wherein the distal portion is proximate thedistal end of the elongate shaft.
 13. The method of manufacturing anintravascular catheter as in claim 11, wherein the shaped distal portionincludes an inner polymeric layer having a melt temperature and an outerpolymeric layer having a different melt temperature, and wherein theinner polymeric layer of the curve shaped portion is generally free ofthe residual stress imparted during the step of shaping the distalportion as a result of the step of heating the shaped distal portion ata temperature at or above the melt temperature of the inner polymericlayer.
 14. The method of manufacturing an intravascular catheter as inclaim 11, wherein the shaped distal portion includes an inner polymericlayer having a melt temperature and an outer polymeric layer having adifferent melt temperature, and wherein the outer polymeric layer of theshaped distal portion is generally free of the residual stress impartedduring the step of shaping the distal portion as a result of beingsubjected to heat at or above the melt temperature of the outerpolymeric layer.
 15. The method of manufacturing an intravascularcatheter as in claim 11, wherein the shaped distal portion includes aninner polymeric layer having a melt temperature and an outer polymericlayer having a different melt temperature, and wherein both the innerand outer polymeric layers of the shaped distal portion are generallyfree of the residual stress as a result of being subjected to heat at orabove the melt temperatures of both the inner and outer polymericlayers.
 16. The method of manufacturing an intravascular catheter as inclaim 11, further comprising the steps of: providing a sleeve; anddisposing the sleeve about the distal portion while heating the distalportion to a temperature at or above the melt temperature.
 17. Themethod of manufacturing an intravascular catheter as in claim 11,wherein the sleeve has a melt temperature greater than the melttemperature of the polymer.
 18. The method of manufacturing anintravascular catheter as in claim 11, further comprising the steps of:providing a mandrel; and disposing the mandrel within the lumen of thedistal portion while heating the distal portion to a temperature at orabove the melt temperature.
 19. The method of manufacturing anintravascular catheter as in claim 11, wherein the distal end of theelongate shaft has a distal end surface, and wherein the mandrelincludes a cap abutting the distal end surface while the distal portionis being subjected to heat at or above the melt temperature.